In the related art, there is a wireless communication device capable of performing wireless communication such as by Bluetooth®. When communication with an external device is not performed for a certain time period in the wireless communication device, power saving control in which a communication function is turned off is performed by stopping a driving clock or reducing the supply of power. The transition to a power saving state is performed even in a memory unit provided within the wireless communication device while retaining data. At the time of returning from the power saving state, the return to a state before the transition to the power saving state is performed by returning the driving clock and the amount of supplied power to an original value.
However, in some conditions at the time of transition to the power saving state, the return to the state before the power saving state is not performed in some cases. Specifically, when the transition to the power saving state is performed during a read sequence on the memory unit, undefined data may be output as read data from the memory unit at the time of returning to the former state in some cases. Such undefined data can cause unpredictable behavior. Accordingly, there is a need for a technology capable of appropriately returning from the power saving state.